1. Field of the Invention
The present invention relates to dental implants which replace natural teeth, particularly to be used as support for oral restorative prostheses which include crowns, fixed partial dentures, removable partial dentures, or full dentures.
2. Description of the Related Art
Dental implants to replace natural teeth comprise basically three components. First, the implant, which is surgically placed into the mandibular and/or maxillary bone. Second, the abutment, which is mounted on the implant after bio-integration of the implant and which serves as a retainer for the prosthesis. Third, the oral restorative prosthesis, which is placed over the implant abutment. One of the latest implant techniques involves the use of hollow-cylinder and/or hollow-screw implants. See articles by Andre Schroeder et al, The New Concept of ITI Hollow-Cylinder and Hollow-Screw Implants, Parts 1 and 2 of Volume 3, Number 3, 1988, The International Journal of Oral and Maxillofacial Implants. A basic concept of parallelism with respect to the existing teeth, or in this case implants, must exist. This invention allows for proper path of insertion or retrievability of the prosthesis over the supporting structure (whether a natural tooth or an implant). The problem which many times arises is that the implant cannot be placed in a substantially parallel relationship to other existing teeth or implants. Therefore, the correction for this parallelism defect must be addressed at the time of mounting the abutment to allow proper prosthetic insertion and retrievability.
At this time, many implant manufacturers attempt to solve this problem by producing many different specific components as documented in the attached product catalog of the Core-Vent Corporation, page 13. A large variety of these abutments exist, but they address only a few very specific situations. When it becomes necessary to change these abutment shapes in order to resolve the specific problem of lack of parallelism, the following process takes place: (a) modifying either a gold-coping abutment or acrylic pattern for an abutment by cutting it down to the appropriate shape; (b) wax or acrylic is then added to modify the structure; (c) when correct parallelism is achieved, the abutment is then cast in gold, and adapted to the existing implant. This results in implant manufacturers having to offer several different abutments to try to overcome the lack of correct angulation, and requires extensive time and work from the dentist in adapting it to the existing situation.
One approach to correct the lack of parallelism is to provide an abutment with a set screw as documented on page 7 of the brochure issued by "O" Company, Inc., Albuquerque, N. Mex., a copy of which is attached hereto. However, this approach requires the use of two screws or threaded members (one at the bottom of the abutment to engage the implant and the other one being the set screw) with the consequent mechanical instability. Also, this approach does not permit an accurate anatomical adaptation of the abutment in the area of the free gingival margin. The abutment in the present invention can be worked more easily and with more flexibility, specially when the implant's abutment receiving end is partially or totally submerged in the gingiva (gum). Also, the prior art approach does not permit a dentist to work directly to correct the lack of parallelism if the latter exceeds fifteen degrees. Finally, this approach requires a dentist to keep a large inventory of abutments and components with different degrees of inclination.
Up to now, all implants have a circular cross-section. The point where the prosthesis and the implant attach also has a circular projection. This is not true with the natural teeth that implants are replacing. Usually, the prosthesis over a natural tooth rests over a structure which has a non-circular natural diameter. Therefore, the circular implants and abutments of the prior art are limited in their ability to reproduce anatomical characteristics of natural teeth thereby limiting the desired aesthetic characteristics of the prosthesis.